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ARS Home » Pacific West Area » Albany, California » Western Regional Research Center » Healthy Processed Foods Research » Research » Publications at this Location » Publication #147131
Title: SODIUM BICARBONATE AND THE MICROSTRUCTURE, EXPANSION AND COLOR OF EXTRUDED BLACK BEANS

Author
item Berrios, Jose
item Wood, Delilah - De
item Whitehand, Linda
item Pan, James

Submitted to: Journal of Food Processing and Preservation
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 10/29/2004
Publication Date: 10/1/2004
Citation: Berrios, J.D., Wood, D.F., Whitehand, L.C., Pan, J. 2004. Sodium Bicarbonate and the Microstructure, Expansion and Color of Extruded Black Beans. Journal of Food Processing and Preservation. 28(5):321-335.

Interpretive Summary: Sodium bicarbonate is a leavening agent used in the bakery industry to enhance product physical properties, such as expansion. Scanning electron micrographs of cross sections of black bean extrudates were able to illustrate the change in volume expansion with an increase of sodium bicarbonate in the extrudate. The measured change in diameter and expansion of extrudates with sodium bicarbonate addition may be explained by the increase in number of air cells within the extrudate and the increase in pores in the gelatinized starch matrix. Extrusion conditions, which involved the use of heat and moisture, provided the necessary conditions for the release of carbon dioxide from sodium bicarbonate during processing. Expansion ratio increased 2 folds at the nod and 1.8 fold at the area between the nods, between the control extrudate and extrudate with 0.5% sodium bicarbonate addition. Analysis of color data showed no significant change in lightness (L*), color (hue) or vividness/dullness (chroma) across levels of sodium bicarbonate for non-extruded flours. Significant differences in these parameters were observed between the non-extruded and extruded flours. The color of extruded flours was considered acceptable for the fabrication of snack type foods.

Technical Abstract: Seed microstructure provides complementary information to physico-chemical determinations. Scanning electron micrographs of cross sections of black bean extrudates, illustrated the change in volume expansion with an increase of sodium bicarbonate (NaHCO3) in the extrudate. This increase in volume expansion was enabled by the increase in air cell size and corresponding decrease in air cell wall thickness with additional levels of NaHCO3. The measured change in diameter and expansion ratio of extrudates with NaHCO3 addition may be explained by the increased in number of air cells within the extrudate and the increase in pores in the gelatinized starch matrix of air cell walls. Extrusion conditions, which involved the use of heat and moisture, provided the necessary conditions for the release of CO2 from NaHCO3 during processing. Expansion ratio increased 2 fold at the nod and 1.8 fold at the area between the nods, between the control extrudate and extrudate with 0.5% NaHCO3 addition. Statistical analysis of color data showed no significant change in (lightness) L*, hue or chroma across levels of NaHCO3 for non-extruded flours, and a simple linear regression adequately described changes in L* and hue for extruded flours. However, a curvilinear relationship was needed to explain changes in chroma vs. NaHCO3 for extruded flours, making changes in chroma measurements less easy to interpret, and thus perhaps less useful for the evaluation of extruded bean flours.